During 2009 the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted reconnaissance interpretive mapping of permafrost in Alaska Highway Corridor Segment 3, a 12-mi-wide (19.3-km-wide) corridor that straddles the Alaska Highway through the Northway-Tanacross Lowland and the southern Yukon-Tanana Upland from Tetlin Junction to the Canada border. This work was an extension of permafrost mapping done in Alaska Highway Corridor Segment 1 from Delta Junction to Dot Lake in the Big Delta and Mt. Hayes Quadrangles during 2006-2007 and Alaska Highway Corridor Segment 2 from the Robertson River to Tetlin Junction in the Tanacross Quadrangles during 2008. Primarily, we inferred the extent of permafrost and ice content by interpreting ~1:65,000-scale, false-color infrared aerial photographs taken in July 1978 and August 1981.

Supplemental_Information:

To enhance print quality, this publication utilized a vector topography dataset. The topography dataset is not included with this release. The DGGS metadata standard extends the FGDC standard to include elements that are required to facilitate our internal data management. These elements, referred to as "layers," group and describe files that have intrinsic logical or topological relationships. The layers listed below are present as ArcGIS shape files. Layers are named to correspond with the names of the files. Attribute information for the following layers (entities) is included in this metadata file under the "Entity_and_Attribute_Information" section. Unit information and descriptions are included on each map sheet. Each layer is listed and described in detail under its own heading starting "Entity_Type_Label."
Layers include:

Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.000001
Ordinates (y-coordinates) are specified to the nearest 0.000001
Planar coordinates are specified in meters

The horizontal datum used is North American Datum of 1927.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378206.4.
The flattening of the ellipsoid used is 1/294.9786982.

This research was supported by Alaska State Capital Improvement Projects funding. The authors gratefully acknowledge the helpful review by M. Torre Jorgenson, and able cartographic assistance by James Weakland.

This report and map are a part of ADGGS's Alaska Natural Gas Pipeline Geology and Geohazards project, funded by the state legislature. They show an interpretive evaluation of the presence or absence of permafrost in the study area. The study was done in anticipation of the proposed natural gas pipeline along the Alaska Highway corridor, as a preliminary look at the expected distribution of permafrost based on air photo interpretation. The work was designed to serve as the springboard for the detailed work which would be required if a pipeline were to be built along this corridor. Because of the dearth of subsurface data in most of the map area, our permafrost designations should be considered tentative until validated by multi-year ground-temperature measurements at a depth below the level of annual temperature variation.

Aerial photograph interpretation and compilation of existing work. DGGS authors compiled geologic data from published and unpublished mapping of the target region and adjacent regions. Stereo pairs of ~1:65,000-scale, false-color infrared Alaska High Altitude Aerial Photographs (AHAP) taken in July 1978 and August 1980 were used to interpret the presence and condition of permafrost. Interpreted proxy data include vegetation, slope and aspect, landforms, geology, local drainage, and terrain features. Unit boundaries were drawn by hand onto acetate overlays, using a magnifying stereoscope. Overlays were registered to aerial photos using tick marks on the photos. The air-photos and scanned overlays were orthorectified, photomosaiced and georeferenced using Orthomapper 3.6. Permafrost unit boundaries were digitized on-screen into ArcGIS 9+ from the orthorectified overlays at a scale more detailed than 1:63,360, using a combination of a USGS topographic 1:63.360 map layer and the air-photo photomosaic layer to verify the position of the lines. Permafrost map polygons and lines were then edited and attributed using ArcMap 9 and ArcMap10.

Data sources used in this process:

Brown and others, 1997

Ferrians, 1965

Ferrians and others, 1969

Kreig and Reger, 1982

Reger and others, 2008

Reger and Hubbard, 2010

USGS Tanacross A-1, 1952 - minor revisions 1971

USGS Tanacross A-2, 1955 - minor revisions 1972

USGS Tanacross A-3, 1948 - minor revisions 1978

USGS Tanacross B-3, 1949 - minor revisions 1964

USGS Nabesna C-1, 1955 - minor revisions 1963

USGS Nabesna D-1, 1952 - minor revisions 1967

USGS Nabesna D-2, 1955 - minor revisions 1978

USGS Nabesna D-3, 1955 - minor revisions 2000

Date: 2009 (process 2 of 4)

Fieldwork - July-August 2009 - DGGS geologists visited localities of varying permafrost conditions in the field to observe surface conditions in order to verify aerial photo interpretations. In addition, they dug several pits, using shovels, to a maximum depth of 1.5 meters to observe soil profiles, determine whether frozen soil was present, and to collect samples for moisture content analysis.

Date: 2011 (process 3 of 4)

Map compilation - The permafrost map was compiled using: field notes from fieldwork process step (above), all known geologic data from previous work in the general region, and additional aerial photograph interpretation. Changes to unit boundaries, after field work, were completed in ArcGIS 9 and ArcGIS 10. The final map layout was created using ArcGIS 10.

This dataset utilizes ~1:65,000-scale, false-color infrared aerial photographs taken in July 1978 and August 1980 to infer permafrost and ice content boundaries. This report uses the definition of permafrost as rock or soil that remains continuously colder than 0 degrees C (32 degrees F) for two years or longer. The presence or former presence of permafrost and the ground-ice content were inferred from several indicators, including vegetation, slope and aspect, land-form, soil type, local drainage, and terrain features, such as open-system pingos, polygonal ground, and thermokarst pits, gullies, and ponds (see lineage reference - Kreig and Reger, 1982). Permafrost classifications in areas that were burned just prior to aerial photography dates are less reliable than in unburned areas because the vegetation was destroyed or significantly altered and, in these areas, interpretation of permafrost was based only on land form and setting, which are less diagnostic than vegetation. During the 2009 field season we excavated and examined soil pits at selected locations to ground check unit descriptions and contacts. Because of the dearth of subsurface data in most of the map area, our permafrost designations should be considered tentative until validated by multi-year ground-temperature measurements at a depth below the level of annual temperature variation. To check attribute accuracy of the digital files we visually compared the original compilation against test plots of the files and corrected discrepancies between the digital geospatial dataset and the original analog as needed. The geologic interpretations presented in this report have undergone technical review by a geologist familiar with the subject of permafrost. We incorporated the reviewer's suggestions into the final draft when deemed appropriate.

The permafrost interpretations were first hand-drawn, using a magnifying stereoscope, onto acetate air-photo overlays at the scale of the air-photos (approximately inch-to-the-mile). The accuracy of the map unit boundary and point locations varies due to the scale and interpretive nature of the mapping and pen line width of approximately 0.001 meter which is equivalent to approximately 1.5 meters on the ground. The hand drawn map unit boundaries and point locations are expected to be accurate to at least 150 meters. Following interpretation, acetate overlays were then individually scanned and orthorectified, using Orthomapper, v. 3.6, and georeferenced. The air-photos were orthorectified, photomosaiced and georeferenced. Permafrost unit and point locations boundaries were digitized on-screen into ArcGIS from the orthorectified overlays at a scale more detailed than 1:63,360, using a combination of a USGS topographic 1:63.360 map layer and the air-photo photo-mosaic layer to verify the position of the lines and points. Map error is induced by: (1) Scanning and orthorectifying air photos and overlays 2) On-screen digitizing from orthorectified overlays. The accuracy of the human operator digitizing polylines and point localities is related to the accuracy of interpretations from the orthorectified photos and overlays. Total horizontal error in the map unit boundaries is estimated to be less than 175 meters.

The shapefiles in this dataset designate ice content, location, and presence of permafrost and pingos discussed in the report. The data set utilizes field observations and air photo interpretations to locate and characterize the permafrost extent and features. It includes geospatial information about units traceable on air photos at a scale of ~1:65000 and/or in the field.

Polygon topology is present and clean on the original geospatial dataset. All polygon features were topologically validated using the ESRI ArcGIS 10 software prior to export to shape file format. The logical consistency of the point files has been visually checked but not systematically verified.

This report, map, and/or dataset are available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).

Use_Constraints:

Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requester or anyone else exceed the fee paid for the electronic service or product.

DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turn around time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.